While we still don’t know for certain whether the next iPhone will feature an indestructible LiquidMetal case, a new patent filing flagged by MacRumors suggests that Apple and LiquidMetal are drawing closer to incorporating amorphous metal alloys into Apple devices.

Specifically, MacRumors notes that the patent proposes a solution to one of the main engineering challenges that Apple has faced with bringing LiquidMetal’s alloy to its products by describing “how molten BMG [bulk metallic glass] could be continuously poured onto a shallow bath of molten tin, where it would flow to form a sheet.” Of course, LiquidMetal iPhone rumors have been around for years now, so there’s no way of knowing just how close the two companies are to making amorphous metal Apple devices a reality.